MLT 181 Unit 3

MLT 181 Immunology Unit 3 summer 26

What is the 1st line of defense that the immune system uses to fight bacteria?

Skin and mucosal barriers

The 3 mechanisms that bacteria use to fight back at the immune system are?

Avoiding Antibody, Blocking phagocytosis, inactivating the complement cascade

Which Lancefield group does S. pyogenes belong to?

Group A

Diagnosis of strep infections that involve early symptoms such as pharyngitis are usually done by ________ and/or ________.

Culture and/or rapid kit tests

2 damaging sequelae of Group A strep are?

And what type of infection do they follow?

Rheumatic fever - after pharyngitis/tonsillitis

Glomerulonephritis - after pharyngitis/tonsillitis or skin infections/pyoderma

The sequelae of Group A strep are diagnosed by serological testing because:

By the time they occur, the organism is no longer present to be cultured or detected by rapid testing

Symptoms of rheumatic fever are?

Fever, joint inflammation, heart inflammation.

BONUS: damage to the heart usually occurs due to cross reactivity of Abs formed against Gp. A strep to heart tissue because myocardial tissue & Gp A strep share antigen similarity.

Tests for rheumatic fever & glomerulonephritis are?

Which one is a screen & not specific for any certain Ab?

ASO, anti-DNase-B, Streptozyme

Streptozyme

Which test is not useful for glomerulonephritis that follows skin infection?

And which test is?

ASO

anti-DNase-B

Bacteria that causes gastric & duodenal ulcers

H. pylori

Infections from H. pylori produce what antibodies?

IgG, IgA and IgM

Majority of tests for H. pylori use antibodies of which class?

IgG

For treatment of H. pylori to be successful, by what percentage does the Ab need to decrease?

>25%

Which test is preferred for H. pylori Abs. & why?

ELISA Cost effective, accurate, sensitive and specific

Major cause or upper respiratory infections and 20% of community acquired pneumonia (often called primary atypical pneumonia)?

Mycoplasma pneumoniae

Outdated test for Mycoplasma is?

And why is it no longer used?

Cold agglutination

Cold agglutinins are not specific for M. pneumonia, some viral diseases & vascular diseases produce them

Cold agglutination test for M. pneumonia involves autoantibodies that react with _______ Ags and react at _____ degrees C.

either I or i

<37 deg C

A false negative may occur in the cold agg test if?

Specimen is refrigerated prior to serum separation

Main two rickettesial infections are?

Typhus and Rocky Mountain Spotted Fever

Febrile agg. test used to detect rickettsial infections is?

Weil-Felix test

Weil-Felix test is based on cross reactivity of pt. Ab. with Ag on what organism?

OX-19 and O-2 strains of Proteus mirabilis

The Widal test is a febrile agg test used for?

And the organism used as the Ag is what?

Typhoid fever

Salmonella

Modes of transmission for syphilis are?

S*xual contact, congenital infections, contaminated needles or blood products

Lesions or ulcers occur in what stage of syphilis?

primary

Agent of syphilis is?

Treponema pallidum

Stage of syphilis where lesions may not be active and where serology is key to diagnosis? This is also the stage where the RPR test is most sensitive for syphilis.

Secondary

Which tests are nontreponemal and are they specific or nonspecific?

Wasserman, RPR, VDRL

NON-specific

RPR stands for ____ and it detects the presence of the Ab, ____ , that forms against ____, an Ag

rapid plasma reagin

reagin

cardiolipin

Lab results show a reactive RPR but a nonreactive FTA. Is this primary, secondary, or tertiary syphilis or another disease such as mono, autoimmune diseases, measles, etc?

This is not syphilis, it is a false + RPR due to another disease

False positives in cardiolipin tests are referred to as______

biological false positives (BFPs)

At which stage of syphilis is the RPR test specific for syphilis?

NONE, it is a NON-specific test

What is added to the antigen suspension in the RPR test to make the test easier to read?

Charcoal

What type of Ag-Ab reaction is seen in the RPR and VDRL tests?

flocculation

False negatives due to prozone effect can be seen in RPR testing which is a lab error due to excessive ___

Serum / Ab

Specs for the RPR test include a rotator with speed of ________ rpm, patient volume of _____ ml serum, and _____ ml of Ag.

100 ± 2 rpm

0.05 ml serum

1/60 ml of Ag

Correct amount of Ag delivered by the needle has to be checked by counting drops delivered. This should be what?

And if the needle is not checked well and too much Ag is delivered this will result in what type of error?

Using a 20 gauge needle and 0.5 ml of Ag suspension, you should get 30± drops

False negative due to postzone

When the RPR test is reactive or just has a “rough” appearance, what is done next?

Quantitative procedure/Titration by diluting the specimen

FTA-ABS and TP-PA are specific tests for syphilis and are what type of test?

Treponemal

The RPR is reactive with a titer of 1:128 and the TP-PA is also reactive. Is this a confirmed or true positive diagnosis of syphilis?

YES

The Ag used in the FTA-ABS test is?

Nichols’s strain of T. pallidum

DFA (direct fluorescent testing) uses labeled antigen while IFA (indirect) what as the label?

Labeled anti-human globulin (AHG)

When diagnosing congenital syphilis, what is the recommended method for testing?

Western Blot test (immunoblotting)

Vector of Lyme disease is?

Ixodes tick

Agent of Lyme disease is?

Borrelia burgdorferi

The CDC recommends 2-tiered testing for Lyme disease. Screening tests are ____ & confirmatory is _____

IFA/EIA for screening and Western blot for confirmatory

In most serology testing which order of testing is preferred?

Sensitive then specific

Toxoplasmosis is a ______ infection

parasitic

Patient serum is mixed with sheep RBCs that have been sensitized with Treponema

pallidum antigens as well as with unsensitized RBCs in a separate well. Agglutination was observed in the well with sensitized red blood cells and not in the well with unsensitized red blood cells. What is the interpretation of these results?

positive for anti-Treponema pallidum antibodies

Name a confirmatory test for syphilis

FTA-ABS

An ASO test was performed, but the result was negative. The patient had shown earlier clinical signs of a streptococcal pyodermic skin infection. What should be done next?

anti-Dnase B testing

A new technologist is busy one night and has to perform an RPR on a serum sample. He does not calibrate the needle delivering the antigen and the needle is delivering a larger volume of antigen than it is supposed to. What kind of error can this cause on the test result?

laboratory-induced false-negative due to postzone

A 32-year-old heterosexual male presents to the physician with a 3-day history of multiple skin lesions located on his body and his mucous membranes. He hasn’t felt well and has a low-grade fever. The patient cuts down trees in Massachusetts for a living. He is single, has had multiple sex partners, and does not use condoms. Here are the results of his laboratory tests: rapid plasma regain-reactive 1:128; Treponema pallidum-particle agglutination assay-reactive, Borrelia burdorferi IgM= <1:8; Rickettsia rickettsii IgM< 1:8. This patient has:

Syphilis

A patient has a reactive RPR at a titer of 1:128 and a reactive TP-PA. What does this indicate for the patient?

true-positive diagnosis of syphilis

One symptom of rheumatic fever is:

heart inflammation

One symptom of glomerulonephritis is

kidney failure

Which increase in antibody titer best indicates an acute infection?

from 1: 64 to 1:128